Optical Inspection Systems for Axisymmetric Parts with Spatial 2D Resolution

The article proposes a solution to the problem of increasing the accuracy of determining the main shaping dimensions of axisymmetric parts through a control system that implements the optical method of spatial resolution. The influence of the projection error of a passive optical system for controlling the geometric parameters of bodies of revolution from the image of its sections, obtained by a digital camera with non-telecentric optics, on the measurement accuracy is shown. Analytical dependencies are derived that describe the features of the transmission of measuring information of a system with non-telecentric optics in order to estimate the projection error. On the basis of the obtained dependences, a method for compensating the projection error of the systems for controlling the geometry of the main shaping surfaces of bodies of revolution has been developed, which makes it possible to increase the accuracy of determining dimensions when using digital cameras with a resolution of 5 megapixels or more, equipped with short-focus lenses. The possibility of implementing the proposed technique is confirmed by the results of experimental studies.

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STUDY OF DIGITAL CAMERA CALIBRATION ON A FLAT TEST OBJECT

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xliii-b2-2020-29-2020 ◽

2020 ◽

Vol XLIII-B2-2020 ◽

pp. 29-33

Author(s):

A. V. Govorov ◽

A. G. Chibunichev ◽

S. B. Makarov

Keyword(s):

Camera Calibration ◽

Test Object ◽

Experimental Studies ◽

Digital Camera ◽

Image Plane ◽

Calibration Method ◽

Digital Cameras ◽

Calibration Accuracy ◽

Spatial Test ◽

Method Accuracy

Abstract. The paper presents a method for calibration of digital cameras based on the use of a flat test object. The main distinctive feature of this method is that the camera is fixed and does not change its position in space. A series of images of a flat test object (for example, a chessboard) is taken at various distances and inclination of the test object. One should tilt the test object relative to the image plane in order to avoid ambiguity in solving the problem. All these images are measured separately, and processing is performed together, counting them as one image with common exterior orientation elements. Experimental studies have shown sufficient efficiency of such calibration, which is easily implemented and gives positive results in comparison with the classical calibration of the camera on a spatial test object. The results of experimental studies on real images have shown that proposed calibration method gives the comparable with conventional method accuracy. Thus, it is possible to use simple and cheap flat calibration test object instead of spatial one. To achieve the maximum result in camera calibration accuracy, use this method to tilt the chessboard at angles in the range of 30–40 degrees to the optical axis of the camera being calibrated.

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АКУСТИЧНА ПОМІТНІСТЬ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ З СИЛОВИМИ УСТАНОВКАМИ НА БАЗІ ПОРШНЕВИХ ДВИГУНІВ

Open Information and Computer Integrated Technologies ◽

10.32620/oikit.2020.88.05 ◽

2020 ◽

pp. 62-80

Author(s):

В. В. Руденко ◽

И. В. Калужинов ◽

Н. А. Андрущенко

Keyword(s):

Control System ◽

Internal Combustion Engine ◽

Power Plants ◽

Combustion Engine ◽

Spectral Characteristics ◽

Experimental Studies ◽

Internal Combustion ◽

Detection Range ◽

Acoustic Signature ◽

Static Conditions

The presence in operation of many prototypes of UAVs with propeller propellers, the use of such devices at relatively low altitudes and flight speeds makes the problem of noise reduction from UAVs urgent both from the point of view of acoustic imperceptibility and ecology.The aim of the work is to determine a set of methods that help to reduce the visibility of UAVs in the acoustic range. It is shown that the main source of noise from the UAV on the ground is the power plant, which includes the engine and the propeller. The parameters of the power plants influencing the processes that determine the acoustic signature of the UAV were investigated. A comprehensive analysis of the factors affecting visibility was carried out. The power plants include two-stroke and four-stroke engines, internal combustion and two-blade propellers. The use of silencers on the exhaust of the internal combustion engine was considered. The spectral characteristics of the acoustic fields of the propeller-driven power plants for the operating sample of the UAV "Eco" were obtained. The measurements were carried out in one-third octave and 1/48 octave frequency bands under static conditions. The venue is the KhAI airfield. Note that the propellers that were part of the power plants operated at Reynolds numbers (Re0,75<2*105), which can significantly affect its aerodynamic and acoustic characteristics. It is shown that when choosing a UAV control system, one should take into account the fact that two-stroke piston engines are the dominant source in the noise of propeller-driven control systems in the absence of a hood and mufflers in the intake and exhaust tracts. The use of a four-stroke internal combustion engine significantly reduces the noise of the control system. In the general case, the position of the boundaries of the zone of acoustic visibility of a UAV at the location of the observer is determined by the ratio between the intensity of acoustic radiation perceived by the observer from the UAV and the intensity of sound corresponding to the natural acoustic background and depends on the degree of manifestation of acoustic effects accompanying the propagation of sound in a turbulent atmosphere - the refraction of sound waves. Absorption and dissipation of acoustic energy. The calculation and comparison of the UAV detection range was carried out taking into account the existing natural maskers.The results of experimental studies are presented that allow assessing the degree of acoustic signature of the UAV. A set of measures aimed at reducing the intensity of the acoustic signature of the UAV in various regions of the radiation spectrum has been determined.

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A Study on Vision-Based Backstepping Control for a Target Tracking System

Actuators ◽

10.3390/act10050105 ◽

2021 ◽

Vol 10 (5) ◽

pp. 105

Author(s):

Thinh Huynh ◽

Minh-Thien Tran ◽

Dong-Hun Lee ◽

Soumayya Chakir ◽

Young-Bok Kim

Keyword(s):

Control System ◽

Visual Servoing ◽

Tracking System ◽

Experimental Studies ◽

Imaging Geometry ◽

Control Scheme ◽

Decoupled Control ◽

Control Configuration ◽

A New Technique ◽

Pointing Control

This paper proposes a new method to control the pose of a camera mounted on a two-axis gimbal system for visual servoing applications. In these applications, the camera should be stable while its line-of-sight points at a target located within the camera’s field of view. One of the most challenging aspects of these systems is the coupling in the gimbal kinematics as well as the imaging geometry. Such factors must be considered in the control system design process to achieve better control performances. The novelty of this study is that the couplings in both mechanism’s kinematics and imaging geometry are decoupled simultaneously by a new technique, so popular control methods can be easily implemented, and good tracking performances are obtained. The proposed control configuration includes a calculation of the gimbal’s desired motion taking into account the coupling influence, and a control law derived by the backstepping procedure. Simulation and experimental studies were conducted, and their results validate the efficiency of the proposed control system. Moreover, comparison studies are conducted between the proposed control scheme, the image-based pointing control, and the decoupled control. This proves the superiority of the proposed approach that requires fewer measurements and results in smoother transient responses.

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Performance Analysis of Surface Reconstruction Algorithms in Vertical Scanning Interferometry Based on Coherence Envelope Detection

Micromachines ◽

10.3390/mi12020164 ◽

2021 ◽

Vol 12 (2) ◽

pp. 164

Author(s):

Dongxu Wu ◽

Fusheng Liang ◽

Chengwei Kang ◽

Fengzhou Fang

Keyword(s):

Surface Reconstruction ◽

Measurement Accuracy ◽

Experimental Studies ◽

Reconstruction Algorithm ◽

Low Noise ◽

Surface Measurement ◽

Reconstruction Algorithms ◽

Centroid Method ◽

Envelope Detection ◽

Vertical Scanning Interferometry

Optical interferometry plays an important role in the topographical surface measurement and characterization in precision/ultra-precision manufacturing. An appropriate surface reconstruction algorithm is essential in obtaining accurate topography information from the digitized interferograms. However, the performance of a surface reconstruction algorithm in interferometric measurements is influenced by environmental disturbances and system noise. This paper presents a comparative analysis of three algorithms commonly used for coherence envelope detection in vertical scanning interferometry, including the centroid method, fast Fourier transform (FFT), and Hilbert transform (HT). Numerical analysis and experimental studies were carried out to evaluate the performance of different envelope detection algorithms in terms of measurement accuracy, speed, and noise resistance. Step height standards were measured using a developed interferometer and the step profiles were reconstructed by different algorithms. The results show that the centroid method has a higher measurement speed than the FFT and HT methods, but it can only provide acceptable measurement accuracy at a low noise level. The FFT and HT methods outperform the centroid method in terms of noise immunity and measurement accuracy. Even if the FFT and HT methods provide similar measurement accuracy, the HT method has a superior measurement speed compared to the FFT method.

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Collective Losses of Low Power Cage Induction Motors—A New Approach

Energies ◽

10.3390/en14061749 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1749

Author(s):

Elzbieta Szychta ◽

Leszek Szychta

Keyword(s):

Control System ◽

Experimental Studies ◽

Complex Problem ◽

Accurate Estimation ◽

New Approach ◽

Water Pumping ◽

Efficiency Control ◽

Interacting Systems ◽

Cage Induction Motor ◽

Selection Of

Energy efficiency of systems of water pumping is a complex problem since efficiency of two distinct interacting systems needs to be combined: water and power supply. This paper introduces a non-intrusive method of calculating the so-called “collective losses” of a cage induction motor. The term “collective losses”, which the authors define, allows for accurate estimation of motor efficiency. Control system of a pump determines operating point of a pumping station, and thus its efficiency. General estimated performance characteristics of a motor, components of a control system, are assumed to serve selection of a range of pumping speed variations. Rotational speed has a direct effect on motor load torque, pump power and head, and thus on motor performance. Hellwig’s statistical method was used to specify characteristics of estimated collective losses on the basis of experimental studies of 21 motors rated at up to 2.2 kW. The results of simulations and experiments are used to verify validity and efficiency of the suggested method. The method is non-intrusive, simple to use, and requires minimum data.

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Bionic Birdlike Imaging Using a Multi-Hyperuniform LED Array

Sensors ◽

10.3390/s21124084 ◽

2021 ◽

Vol 21 (12) ◽

pp. 4084

Author(s):

Xin-Yu Zhao ◽

Li-Jing Li ◽

Lei Cao ◽

Ming-Jie Sun

Keyword(s):

Imaging System ◽

Color Image ◽

Digital Camera ◽

Frame Rate ◽

Digital Cameras ◽

Structured Illumination ◽

Pixel Resolution ◽

Led Array ◽

Frequency Aliasing ◽

Imaging Sensors

Digital cameras obtain color information of the scene using a chromatic filter, usually a Bayer filter, overlaid on a pixelated detector. However, the periodic arrangement of both the filter array and the detector array introduces frequency aliasing in sampling and color misregistration during demosaicking process which causes degradation of image quality. Inspired by the biological structure of the avian retinas, we developed a chromatic LED array which has a geometric arrangement of multi-hyperuniformity, which exhibits an irregularity on small-length scales but a quasi-uniformity on large scales, to suppress frequency aliasing and color misregistration in full color image retrieval. Experiments were performed with a single-pixel imaging system using the multi-hyperuniform chromatic LED array to provide structured illumination, and 208 fps frame rate was achieved at 32 × 32 pixel resolution. By comparing the experimental results with the images captured with a conventional digital camera, it has been demonstrated that the proposed imaging system forms images with less chromatic moiré patterns and color misregistration artifacts. The concept proposed verified here could provide insights for the design and the manufacturing of future bionic imaging sensors.

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Designing a Color Filter with High Overall Transmittance for Improving the Color Accuracy of Digital Cameras

Color and Imaging Conference ◽

10.2352/issn.2169-2629.2021.29.1 ◽

2021 ◽

Vol 2021 (29) ◽

pp. 1-6

Author(s):

Yuteng Zhu ◽

Graham D. Finlayson

Keyword(s):

White Light ◽

Digital Camera ◽

Color Filter ◽

Digital Cameras ◽

Spectral Transmittance ◽

Optimal Filters ◽

Prior Art ◽

Average Transmittance ◽

Tristimulus Values ◽

Correction Problem

Previously improved color accuracy of a given digital camera was achieved by carefully designing the spectral transmittance of a color filter to be placed in front of the camera. Specifically, the filter is designed in a way that the spectral sensitivities of the camera after filtering are approximately linearly related to the color matching functions (or tristimulus values) of the human visual system. To avoid filters that absorbed too much light, the optimization could incorporate a minimum per wavelength transmittance constraint. In this paper, we change the optimization so that the overall filter transmittance is bounded, i.e. we solve for the filter that (for a uniform white light) transmits (say) 50% of the light. Experiments demonstrate that these filters continue to solve the color correction problem (they make cameras much more colorimetric). Significantly, the optimal filters by restraining the average transmittance can deliver a further 10% improvement in terms of color accuracy compared to the prior art of bounding the low transmittance.

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EXPERIMENTAL STUDIES ON THE DEVELOPMENT OF AN AUTOMATED SYSTEM FOR REGULATING THE SOIL DENSITY USED IN A SEEDING MACHINE

AGRICULTURAL ENGINEERING ◽

10.26897/2687-1149-2021-2-9-15 ◽

2021 ◽

pp. 9-15

Author(s):

ALEKSEI S. DOROKHOV ◽

Keyword(s):

Control System ◽

Automatic Control ◽

Automatic Control System ◽

Power Supply ◽

Experimental Studies ◽

Automated System ◽

Statistical Characteristics ◽

Vegetable Crops ◽

Soil Density ◽

Density Control

Research on the development of an automatic control system for the rolling-in working units is aimed at establishing the reliability and analytical relationships, determining the quality indicators of work in real conditions of the rolling-in working units of a seeding machine, and checking the patterns obtained in the fi eld and identifi ed theoretically. Research on the development of an automatic control system for the rolling implements was carried out when sowing dragee seeds of table beet of the Bordeaux variety with a seeding unit consisting of a Belarus-4235 tractor and a Monopil S15/12 precision seeding machine. The system for automatic control of soil density includes the main hardware and software: actuators for maintaining and deepening the rolling working units, microcontrollers, motor drivers, a non-contact ultrasonic sensor, a power supply unit and a sensor for measuring soil density. The paper presents the results of a study to determine the soil density when sowing seeds of table beet, depending on the moisture content of the soil in the sowing layer. The authors describe research methodology, provide graphical relationships between changes in soil density and the depth of seeding, and comment on the main obtained statistical characteristics of the experiment. As a result of the study, structural, echnological and functional diagrams of a rolling rink with an automatic control system using electronically controlled electric cylinders (linear actuators) have been developed. The optimal parameters of the linear drive of the press roller have been established: power - 50W, power supply - 12V, rod stroke - 200…600 mm, speed - 10…45 mm/s, load - 200…900 N. Experimental studies have shown the applicability of the presented system of the automatic control of soil density, which ensures the optimum density of the seedbed of 1.3…1.4 g/cm³. The described technique can be used to develop a soil density control system when sowing seeds of other vegetable crops.

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Part Monitoring and Quality Assessment of Conformal Additive Manufacturing Using Image Reconstruction

Volume 5B: 42nd Mechanisms and Robotics Conference ◽

10.1115/detc2018-85370 ◽

2018 ◽

Author(s):

Michael D. Kutzer ◽

Levi D. DeVries ◽

Cooper D. Blas

Keyword(s):

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Digital Camera ◽

Image Data ◽

Digital Cameras ◽

Public And Private ◽

The Public ◽

Fused Deposition ◽

Complex Part ◽

Deposition Modeling

Additive manufacturing (AM) technologies have become almost universal in concept development, prototyping, and education. Advances in materials and methods continue to extend this technology to small batch and complex part manufacturing for the public and private sectors. Despite the growing popularity of digital cameras in AM systems, use of image data for part monitoring is largely unexplored. This paper presents a new method for estimating the 3D internal structure of fused deposition modeling (FDM) processes using image data from a single digital camera. Relative transformations are established using motion capture, and the 3D model is created using knowledge of the deposition path coupled with assumptions about the deposition cross-section. Results show that part geometry can be estimated and visualized using the methods presented in this work.

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